Gaming machines which provide players awards in primary or base games are well known. Gaming machines generally require the player to place or make a wager to activate the primary or base game. In many of these gaming machines, the award is based on the player obtaining a winning symbol or symbol combination and on the amount of the wager (e.g., the higher the wager, the higher the award). Symbols or symbol combinations which are less likely to occur usually provide higher awards.
Secondary or bonus games are also known in gaming machines. Secondary or bonus games usually do not require an additional wager by the player to be activated and provide an additional award, such as a bonus award, to the player. In certain known gaming machines, secondary or bonus games are activated or triggered upon an occurrence of a symbol or symbol combination in the primary or base game. For instance, a symbol occurring on the payline on the third reel of a three reel slot machine may initiate a secondary bonus game. That is, these gaming machines include symbol-driven secondary or bonus games which are triggered by the gaming machine. It should be appreciated that since these are game defined symbols or symbol combinations, the frequency and payouts are determined by the game's design and thus are considered an integral part of the game and the characteristic of the game.
The awards provided for such secondary or bonus games are calculated into or taken into account in the total average expected payback of the gaming machine. Thus, the total average expected payback or the total gaming machine return of such known gaming machines is the average expected payback of the primary or base game plays plus the average expected payback of the secondary or bonus game plays.
In designing such secondary or bonus games, game designers must calculate the frequency at which the bonus game is triggered from the base game and the contribution of the bonus game to the overall average expected payback of the gaming machine. Another factor which must be considered in the game design is whether large awards will be offered in the bonus game. Providing large awards in the bonus game is attractive to players. However, if the bonus game contribution to the overall average expected payback is too high, the average expected payback from the base game must be reduced. Reducing the average expected payback for the base game can be frustrating for players who do not obtain or often obtain a bonus game trigger. However, to keep the base game average expected payback high, the frequency at which the bonus game is triggered must often be reduced.
Games in which the bonus game includes high awards require either reducing the frequency of the bonus game trigger or lowering the average expected payback of the base game. If the bonus game is infrequently triggered and the base game has a low average expected payback, players may lose interest in the game or their gaming sessions may end prior to triggering the bonus game. On the other hand, increasing the frequency at which the bonus game is triggered and reducing the size of the bonus game awards can lead to a less interesting game where triggering the bonus game is a routine event.
When the bonus game triggering event is tied directly to specific events in the base game, the frequency with which the bonus game is triggered is difficult to adjust because such changes in the bonus trigger frequency bring significant change to the overall average expected payback of the gaming machine. Another disadvantage of such games where the bonus game is driven by or triggered from the base game is that bonus game play ensues only after the outcome of the base game is known, thereby reducing opportunities for surprise and entertainment.
Certain known gaming machines provide mystery triggered bonus games, which are triggered without any apparent reason to the player. That is, these gaming machines trigger and display a mystery bonus game (and provide a player any mystery bonus award in the mystery bonus game) independent of any displayed event in or based specifically on any of the displayed plays of any base game. Such mystery bonus awards typically account for a smaller contribution to the total gaming machine return and are considered separate from the primary or base game (i.e., these mystery bonus games are said to sit on top of any existing primary or base games and any existing symbol-driven bonus games).
Certain known slot machines adjust the odds of winning awards, such as progressive awards, in bonus games based upon the number of coins or credits wagered. One known way to accomplish this is by adjusting the probability of triggering the bonus game in direct proportion (i.e., linearly) to the wager. If a player wagers 1 credit, the player has a 1 in 25,000 chance of triggering the bonus game. If the player wagers 5 credits, the player has a 5 in 25,000 chance of triggering the bonus game. Once the bonus game is triggered, the odds of winning in the bonus game are static regardless of the wager amount placed.
Another known method for adjusting the odds of winning awards in bonus games is the reverse of the above method. The odds of triggering the bonus game are static and remain unchanged based on the wager. However, once in the bonus game, the probability of winning in the bonus game varies in direct proportion with the wager.
There is a continuing need to provide new and different gaming machines and gaming systems, as well as new and different ways to vary the probability of winning one or more designated awards.